The video shows a guy spraying a flammable substance into an uninflated tire (with the rim sitting in the middle), then setting it on fire which instantly causes the tire to become inflated. What is going on here?
Explosions expand the air around them. The gas expanded rapidly enough to seat the tire and inflate it. IIRC that’s an old trick to reseat a tire.
I don’t see it looking very quickly (on youtube) but I though mythbusters did it too.
They did. And the tire quickly deflates as the air inside cools down.
I’ve only heard of it as a trick to reseat the bead. Did the bead stay seated, I don’t remember.
Mytthbusters video. The myth was inflating and staying inflated.
The aerosol used is starting fluid (ether) and as others said it’s just to seat the ‘beads’ of tubeless tires. You have to immediately keep inflating the tire the regular way to fully seal both beads (sides).
The trick is used if you’re in a situation where you don’t have enough pressure & volume of compressed air in order to get the beads to seat. A typical tire changing machine has a thick, ring-shaped air outlet around the bottom of the tire that blasts a large amount of air into the unseated tire with enough pressure & volume to make the stiff rubber expand and seat the bead. Just an airline connected to the tire’s valve usually can’t do this even with reasonably high pressure (it can’t push a high enough volume of air in fast enough thru the valve stem). Once the bead is (temporarily) ‘seated’ you can finish inflating it and get both beads to seal (pop) into place.
It’s a very unusual thing to do, no shop with a tire machine would ever need to do it. It’s really sort of a stranded-in-the-middle-of-nowhere-with-a-flat kind of thing, and even then you’d still need some kind of air pump to fully seal the beads of the tire…
I have seen the tire guys do this countless times over the years, mostly 20 years ago. Too much either the tire will jump 4 ft off the ground.
It’s also a good way to singe arm hair, eyebrows, and miscellaneous other hair if you don’t have a clip-on chuck for your air hose. Not that I’ve ever done that personally, you know. I’m just saying. :dubious:
I originally heard about this as only the means to seat a truck tire. With big heavy tires getting it to seat with out mechanical assistance is supposed to be impossible, so this was a way to make it a one person job. But it seems like you have to start pumping air in immediately to make it useful. Since first hearing this I’ve heard the myth, that the tire would stay inflated.
it does seat the tire if done right. it also works good on small less rigid tires like wheel barrows and lawn/garden tractors. you need to quickly and gently apply compressed air through the hose.
Not air inside anymore. Assuming the flammable substance was a hydrocarbon like (ether/starting fluid), a large portion of the combustion products is water vapor. Immediately after the burn, the temperature of the combustion products is plenty hot, but the cold rim and tire will rapidly remove heat; as it cools toward room temperature, the water vapor will condense. In contrast to a gas like air that just reduces pressure modestly as it cools, the condensation process lowers the volume of the water by a factor of about 1000. That’s why you can do fun tricks like this.
Quite different from just having a tire full of hot air.
I have done this several times and like has been said can be very dangerouse.
The last time was a couple months ago with a trailer tire that had been flat for a long time and cold where there was no way to hold the tire snug enough to the rim to inflate it, and all I had was a foot operated machanical pump. Being causious, and needing to get air into the tire rapidly after the woof from the either, I failed on the first two attempts, but got the tire to seal.
That video showed a tire/rim combination where the method used was very nessesary, although some basic safety practices like safety glasses and a fire extigusher is highly recommend.